Fluxes of Carbon between Reservoirs

Carbon is released from the lithosphere by erosion and resides in the oceans ca. 10 years before being deposited again in some form of oceanic sediment. It remains in the lithosphere on the average 10 years before again being released by erosion (Broecker, 1973). The amount of carbon in the ocean-atmosphere-biosphere system is maintained in a steady state by geologic processes the role of biological processes is, however, of profound importance 

Chemical weathering of crustal material can both add and withdraw carbon from the atmosphere. This has been discussed in Chapter 8. The oxidation of reduced carbon releases CO2 to the atmosphere, 

Silicates also lead to uptake of CO2. Weathering of a non-aluminum silicate like Mg-olivine may be written 

An example of aluminosilicate weathering is the reaction of the feldspar albite to a montmor-illonite-type mineral 

The freshwater cycle is an important link in the carbon cycle as an agent of erosion and as a necessary condition for terrestrial life. Although the amount of carbon stored in freshwater systems is insignificant as a carbon reservoir (De Vooys, 1979 Kempe, 1979a), about 90% of the material transported from land to oceans is carried by streams and rivers. 

Garrels and Mackenzie (1971) calculated global river loads based on Livingstone s (1963) data. From these figures, Kempe (1979a) deduced the following fluxes of carbon to the oceans transported by rivers  

In the weathering of carbonates, 1 mole of rock CO2 is mobilized for each mole of atmospheric CO2 

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